LM-1 Installation in Early 911- MFI

[304065]

Well, I finally got around to installing the LM-1 this past Saturday.

After consulting the experts, I determined that the best place to locate the sensor bung is in the INLET to my sport muffler. This is only slightly downstream of the header, wouldn't require removal of the SSI's (with attendant risk of snapping studs) and is cheaper than fixing the SSI's if things didnt' go well.

The first step was removing the rear bumper to provide muffler access. It's not going back on: I have a fiberglass 911R-style to replace it. It weighs a great deal, besides.

With that complete, it was time to make a couple holes in the muffler inlets. The manual dictates that the sensor NOT be installed at the 6:00 position, as the resultant water accumulation will destroy it, and also, I tend to drive off the track a lot, and I wanted to protect the sensor. So I decided to put it at roughly the 9:00 position, inboard, close enough to the "sausage" part of the muffler to be able to clear the flange bolts. (Egad, actually PLANNING AHEAD?)

The muffler is of unknown origin, and I think it's aluminized steel. I punched the inlet, drilled a pilot hole, and enlarged the hole to 16.4mm with a Unibit. This is roughly the diameter of the sensor probe.

I put one in each side: the LM-1 only ships with a single sensor, but I wanted to be able to switch it from side to side to monitor both banks.


I used a wire wheel to remove the aluminized coating and to clean the area.

It was off to the local garage to weld it up. I took it a local service station, where, wonder of wonders, the fellow who worked there used to crew on an IMSA team back in the early '80's. He did a fine job with a MIG welder (mild steel filler rod) of putting the bungs in. We did it "917 Style" with plenty of bead for strength. He fish-mouthed the bungs with a die grinder. CAUTION: make sure you have the bungs aligned properly with the holes, otherwise the sensor won't go in. We actually used an old sensor to align with during welding.

[304065]

I was completely taken aback, by the way, that the mechanic refused to charge me for the welding. He said, "Invite me up to Lime Rock when you go." It restored my faith in the decency of mankind, no kidding.

That complete, it was time to put the sensor in and TEST. It threads in easily with a little anti-seize paste.


I'll route the wires neatly later, it's time for TESTING!

At 2000 RPM, look at THIS! This gives a whole new meaning to CHECK MEASURE ADJUST!



Gratuitous shot of the old girl with multiple contusions after this season. Back into the shop for the winter!

[Lukesportsman]

John,
I still haven't used the LM1 on the MFI yet. Let us know how things go and what type of A/F curve you are able to obtain at home using this instrument. If possible, give us some feedback on how the performance compares before and after adjustments.

Are you just looking at real time numbers or are you downloading them and plotting them on the computer?

[304065]

Luke,

I'll post a complete writeup on experimentation. I have Logworks and the RPM cable, and plan to log AFR, RPM, Intake Temp & Oil Temperature eventually. I also have a DL-90 data logger that has some aux inputs, so I can see logging AFR and RPM at various points on the track.

Noah,

Thanks for the tip on the antiseize. I've got to get some new exhaust gaskets and will order a new tube of the copper stuff.

[klatinn]

Hi John,

Pretty soon you will be able to use both bungs. The LC-1 (in the last stages of production release) will allow you to datalog both banks simultaniously.

Regards,
Klaus

[304065]

Klaus, thanks for the information. I am extremely pleased with the product and the documentation is excellent.

Anybody want to buy a used Gunson Gastester Professional?

[klatinn]

Hi John,

Thanks for the product endorsement. Looking at the picture of the LM-1 display I noticed that the last square of the 'instant lambda bar' looks faded. This means that it is rapidly switching on and off. This happens when there are fast fluctuations of mixture (different AFRs between cylinders). You might have uneven mixture distribution between cylinders on that bank.

Regards,
Klaus

[Neilk]

I was thinking that the next project would be to put bungs on each cylinder so you can tune them individually.

That's a great look car John. I look forward to hearing more about your projects.

[Overpaid Slacker]

Looks great, Kos. Congrats. Don't forget the tricks you learned before we get to installing mine in the Spring!

JP

[304065]

Klaus, thanks for the tip!

No DOUBT I have uneven mixtures between the cylinders. The correlation is probably all over the place. The difficulty I have is setting the throttle plates to exactly the same angle BEFORE correcting with the airbleed screws. At least now I have a way to tell!

Neil,

Thanks for the kind words. I had considered a sensor on each jug, but the difficulty in fabrication, plus the cost of the sensors ($60 each) made that out of my reach for now. Stay tuned for updates.

JP,

Turbos are a whole 'nother ball of wax, but I assume you already have the bung for your HAL meter, so installation should be a snap- just unscrew (probably destroying in the process) the old narrowband sensor, screw in the wideband, and run the wires. We could mount the LM-1 box on your ROLL CAGE . . .

[svandamme]

John, rebump on your thread there

you went for 2 sensors on both inlet's of your muffler
but i assume you can get a pretty good readout if you just put 1 sensor bung on the muffler itself? i was thinking to put one on the exit pipe, close to the muffler itself (so it's out of view)

i realize that this setup would not give me seperate readings for the left and right side of the engine , but this would be a practical , and usable location for the sensor , right?

i mean, if i sort out the correlation on the intake stacks with a unisyn ... and get those in good shape then the AFR should allready be pretty equal for all cyllinders as well? aside from having injectors not putting out equally , but that's not a tunable item anyway

[304065]

Stijn,

The question is, how certain are you of the correlation? I am by no means ever certain.

It's true that if you have every stack pulling the same, that means you have the cross-link adjusted properly, and there would be no need to adjust the stacks side-to-side. We know that one bank might run hotter than the other due to the direction of the fan's rotation, but I really doubt you could tune for it-- the error caused by reading one bank with the sensor, then switching to the other bank, would probably be too great or send you in the wrong direction.

But my rationale for putting the sensor in the inlet was this: plenty of heat to keep it clean, it's higher than the outlet so more protected when I drive off track (which I do with frequency), and this last point, which I learned from Klaus:

The resolution of the Bosch sensor is SO high that you can actually detect mixture fluctuations from the discrete exhaust pulses in the bank of three cylinders. If correlation is off between individual stacks you can actually see the final bar of the lambda readout flickering-- which is a clue to go back and re-check correlation between the stacks. By reducing the number of cylinders feeding in you actually amplify the variations-- monitoring all six might smooth the readout.

If I had unlimited dollars I would have individual sensors mounted in EACH SSI tube and monitor six channels simultaneously.

[svandamme]

well, i'm getting mine tomorrow
i'll go for the single sensor and see how it goes
my engine is running crappy at the moment , and i have no data at all other than gut feelings.. so any data will be an improvement for me
i can alsways plug the hole and mount two sensors later on

[304065]

Stijn,

Good luck! Tuning with the LM-1 is a BIG help-- you finally get some actual data.

Once you get it set up, you can actually measure the impact of a single click of the adjuster and see the results. It's the biggest single help for tuning MFI since the synchrometer!

[bkreigsr]

Thanks for the post John, makes me feel guilty for driving the MFI and not knowing exactly what's going on back there, fuel/air ratio wise, outside of what the Gunson was telling me where I was at idle. Let us know where you tie into the tackometer with the LMA-2 cable.

[}{arlequin]

how did i miss this thread? Nice job John. Could this be helpful in running carbs too?

[svandamme]

oooh , came to work this morning, and the box was waiting at the reception for me, it's amazing how a plastic little box with some wires can be so sexy... i'm sitting here, ranting about sniffing my tailpipe, my collegues are looking worried ...

[svandamme]

had the bung welded in , at the end-pipe
fit's perfectly , plenty of room above the muffler for the sensor

[mjshira]

John, does modern engine management perform this function? what kind of degree of benefit are you getting?

thanks

[tobluforu]

This is an old thread, obviously, but what I would like to know is if anyone who has done this has found a sweet spot in regards to MFI and a/f ratios. I know these like to run rich, but at what rpm is the best to take measurements, is it just like my Saab where I run it at WOT and adjust accordingly, probably not?